[QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

[Christoph Wolf]

Dear all,

I have a fairly general question and I hope I can pick someone's brain:

If an insulator or semiconductor is doped with a metal narrow bands
determined by the crystal field emerge and often the fermi level lies
within one of the bands, i.e. the "bands cut the fermi level", which is
often called a characteristic of a conductor but in the bigger picture no
electrons would be able to cross from the VB to the CB, i.e. the host
system is an insulator.

When attempting to calculate the phonons of a Mg7O8Fe supercell the
dieletric constant (in the case of pure MgO eps~3.1) cannot be computed

     Electric Fields Calculation
     ik   1 ibnd   0 linter: root not converged  2.635E-07
....
..

     End of electric fields calculation

          Dielectric constant in cartesian axis

          (******************       0.000244141      -0.001708984 )
          (      -0.000244141******************       0.000244141 )
          (      -0.000732422       0.000732422****************** )

And I am wondering if that system should be treated as a metal instead
(epsil    = .false.,) during the phonon run?

--
&inputph
  prefix   = 'MgO',
  epsil    = .true.,
  alpha_mix(1) =0.4
  alpha_mix(2) =0.4
  fildyn   = 'MgO.dyn',
  ldisp    = .true.
  fildvscf = 'dvscf'
  amass(1) = 24.30500
  amass(2) = 15.99900
  amass(3) = 55.84500
  outdir='./',
  nq1=6,
  nq2=6,
  nq3=6,
  tr2_ph   =  1.0d-12,
 /

Any hint is welcome!

Thanks in advance for your help and a nice Sunday everyone!

Chris
-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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